So it's been about a week and a half since this flight, and I'm still not quite sure what to make of it. It was an interesting flight for sure, and the data available is un-ending. It will be a month or more before everything is digested.
On the good side, we got the rocket to the launch and on the pad with no major incidents. I'm proud of that, as this project is right at the limit of the complexity that I can manage. We got all three motors lit - including a Gorilla moonburner at 36,000 feet - and apogee was at 130,570 feet, my highest flight. And like I said, there's lots of data to analyze. On the down side, I lost the second stage of the rocket - bummer. In addition, the first stage did not separate as planned, so the vertical stabilization system didn't have a chance to function. Consequently, the rocket flew at a bit of an angle, and it was a long walk to recover the third stage. What's interesting though is that there are things that happened where I thought I was unlucky, where maybe it will turn out the other way around - and vice versa. I don't know the ending to the story yet.
Before starting in on the data, I should thank a few people. First off, the flight wouldn't have happened without Zebedee's help (thanks Martin). Steve and Manny made some key contributions at the pad, and I'm sure glad Alex captured the video. Tony, as usual, set hands on several of the parts and tried his best to find the second stage, and Deb took us out in her 4-wheel drive vehicle for a little more searching. There are about a hundred other people that contributed to this in some way - thanks! My wife helped too (trust me on this).
So, to the data. There will be some on-board video for this flight, including a side-facing camera and an upward-facing camera, mounted on the first stage. The video is being processed, but I think you will find it pretty interesting. It was a wild ride.
Attached is a data plot from the EasyMega in the third stage. The first event in the flight was a bit of a turn about a second after launch. You can see that in the video Alex took. I suspect that this was wind shear. The rocket straightened up a little, but it was wobbling somewhat. At four seconds, there was a separation charge that was supposed to separate the first stage from the stabilization spool, leaving the stabilization spool to vertically stabilize the rocket during the coast period until the second stage lit. You can see that the charge fired, but separation didn't occur. The attached picture shows the video frames just before and after this separation charge. The parts tried to separate, but didn't make it. It is possible that the wobbling of the rocket at this point tightened this joint and prevented separation. This is one of those events where I'm not quite sure yet if I was lucky or unlucky.
With the draggy booster still attached, the rocket slowed down quicker than expected. When the second stage lit, the rocket had slowed to under 300 ft/s (was supposed to be more like 750 ft/s). I guess I'm lucky that the motor didn't take any longer than it did to come up to pressure, but the rocket did develop a little tilt just before the motor lit.
I had originally intended to light the third stage about 40 seconds into the flight and at 40,000 feet. Due to the frisky upper-level winds, I attempted to reduce this by about 10 seconds. Unfortunately, I programmed the EasyMega incorrectly (in the way that I incorporated an altitude check). Check back a few posts where I posted the program. The problem in the logic is obvious - now - but I overlooked it and no one else caught it. The net effect was to delay the third stage igniter by about 4 seconds past the point where I wanted it to light (lucky - it could have been worse). Then, the motor took over 6 seconds to come up to pressure, and lit at 36K feet. Those factors pretty much got me back to the original flight plan. So, off to apogee we went, and a pic on the way there is attached.
The above summary doesn't begin to capture all of the stuff that actually happened on this flight. Maybe I'll post more later if we can separate cause and effect, or post what will eventually be a rather long list of lessons-learned. And I will post the on-board video when it's ready.
Jim
